Dolby Pro Logic

Dolby Pro Logic is an analog surround sound system developed by Dolby Laboratories in 1976 for cinema sound systems as Dolby Analog SR. The Analog SR format was adapted for home use in 1986 as Dolby Surround which was replaced by the newer Pro-Logic system.

Both Dolby Surround and Pro Logic are based on basic Matrix technology; four channels of sound are encoded into an ordinary stereo sound track by using phase shift techniques. A decoder/processor "unfolds" the sound into 4.0 sourround – left and right, center, and a limited-range mono rear channel – while systems lacking the decoder playback the audio as standard Stereo.

In 2000, Dolby introduced Dolby Pro Logic II, essentially a redesigned version of Pro Logic which adds an LFE (subwoofer) and stereo surround channels to Pro-Logic sourround. The Pro-Logic II system also features modes designed specifically for Music and Gaming, and it is frequently used on video games for Sony's PlayStation 2, Microsoft's Xbox and Nintendo's GameCube as an alternative to digital technologies like Dolby Digital. A newer Dolby Pro Logic IIx system is also now available, which can take stereo, Pro-Logic and Dolby Sourround (sometimes called Dolby Stereo Surround) source material and up-convert it to 5.1/6.1 channel surround sound.

Pro Logic Vs. Dolby Sourround

Dolby's earlier Dolby Surround format and Dolby Pro-Logic are almost identical in practice, as both use Matrix technology to extract extra channels from stereo-encoded audio. However, Pro Logic uses advanced algorithms, superior to the earlier Dolby Surround system, in order to not only extract the extra channels, but to also improve steering and discreteness between the front channels.

Dolby Decoding Matrices

External links

• Dolby's official site
• A Listener's Guide To Pro Logic II